French investigators look at a map indicating actions in the search for wreckage from the missing MH370 airliner on Réunion Island, Aug. 14, 2015. Photo: Getty Images

The search for missing Malaysia Airlines Flight 370, nicknamed MH370, has officially swept 70,000 of the 120,000 square kilometers of the Indian Ocean floor it intends to check for evidence. According to an operational search update from the Australian Joint Agency Coordination Centre posted this week, investigators have been struggling with "unfavorable" conditions that have complicated their efforts to find the mysterious aircraft. But they could soon move past them.

"Weather continues to impact ... search operations, but conditions are expected to be improved over the coming months," the update read. "The safety of the search crews, as always, remains a priority, and the vessels and equipment utilized will vary to reflect operational needs."

MH370 vanished March 8, 2014, en route from Kuala Lumpur to Beijing. The 239 people on board are presumed dead, and the plane -- a Boeing 777 -- is presumed to have crashed, but little debris has turned up to support that theory. The only discovery came this past July, when a flaperon wing fragment was found on Réunion Island.

Two survey vessels, the Fugro Discovery and Fugro Equator, were scanning the ocean floor for debris. The Equator was scheduled to return to the Australian port city of Fremantle to resupply while the Discovery used a towed sonar system to search, but the Discovery hit a snag Thursday. A crew member was diagnosed with likely appendicitis, forcing the ship also to return to Fremantle, according to the agency.

Meanwhile, aviation expert David Learmount wrote on his blog that he expected the next phase of the search to get "interesting" because "logic says they must be getting close," based on the large area swept without results. Also, Boeing 777 captain Simon Hardy calculated where he thought the flight went down, and "the search sector that Fugro Discovery has just begun to trawl encompasses Hardy’s predicted position for MH370," Learmount wrote. He added: "By 3 December Fugro Discovery expects to have completed the search of the area containing, according to Hardy’s calculations, the wreck of MH370 and the remains of those who went down with it."

If the plane is found, Australia will work with Malaysia and China to recover it.